Telephone-transmitter



(No Modl.)

' 0. D. HASKINS.

TELEPHONE TRANSMITTER.

Patented 001;. 16, 1883.

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' UNITED STATES PATENT, OF ICE.

CHARLES D. HASKINS, OF NEW YORK, Y., ASSIGNOR TO THE WESTERN ELECTRICMANUFACTURING COMPANY, OF CHICAGO, ILLINOIS.

TELEPHONE-TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 286,923, dated October16, 1883.

(No model.)

To all whom it may concern.-

Be it known that I. CHARLES D. HASKINS, of New York, New York, havediscovered a certain new and useful Improvement inTelephone-Transmitters, of which the following is afull, clear, concise,and exact description.

My invention relates to the method of inducing voice-currents in atelephone-line from a local circuit by means of a diaphragm and movablecontacts and an induction-coil. Heretofore the current has been sentthrough the primary of the induction-coil in one direction or inreversals, the primary consisting of a single wire.

My improvement consists in winding the primary of the induction-coil inbranches, the branches being wound so that the current will divide andpass in opposite directions through the primary, the points of variableresistance being soarranged that when the diaphragm is set in vibrationthe strength of the current in the branches of the primary will vary.The resultant ordifferential of the variations in the branches willinduce reversed voice-currents in the line passing through the secondaryof the induction-coil.

In the drawing I have shown my improved transmitter in section, and adiagram of the circuits through the induction-coil.-

The diaphragm a is japanned on both sides, and insulated from the frameI) by'means of the rubber c, which may be placed around the edges of thediaphragm, so as to lap toward its center on both sides, as shown. Thecontact points or electrodes, d 6, may be of platinum, and aresupported, respectively, on the opposite side of the diaphragm by thesprings f g. The springs hold the contact-points against the pieces ofcarbon h t, which are supported by the springs 70 Z. The contact-points0 should be adjusted to the carbon pieces so that normally theresistance at one point will be about the same as at the other. Tracingnow the circuit of the current from the battery as indicated by thearrows,wefindt\vo branches, m n, passing through the induction-coil inopposite directions to the contact-points d e. The branch circuits passthence through the carbon pieces and the springs is Z, and unite in theframe,which is connected with the other pole of the battery, as shown.Vhen the diaphragm is set in vibration by the voice, it is evident thatthe resistance of the carbon points in the two branches will vary withthe vibrations. The effective current through the branches of theprimary will be measured by the difference between the strength of thecurrent in the two branches at any given instant. The current will, itis evident, now be stronger in one branch and now stronger in the other,

and thus the effective current of the differential will be in reversals,and consequently the induced voice-current in the main line will be inreversals corresponding to the differential of the current in the twobranches of the primary.

I claim The combination of the following elements: diaphragm a, frameI), insulating substance 0, contact-points d 6, supported by springs fcarbon pieces h i, supported by adjustable 7o springs in Z, and thebranches mat of the primary of the induction-coil, substantially asshown and described.

CHAS. D. HASKINS.

WVitnesses:

WM. J. ARMSTRONG,

WM. P. ILLENSWORTH.

